eNodeB

An eNodeB, or Evolved Node B, is the base station element of the LTE network's E-UTRAN. It terminates the air interface to user equipment (UE) and provides the radio access network functions and control for the UEs. The eNodeB connects to the Evolved Packet Core (EPC) over the S1 interface and to neighboring eNodeBs over X2; the radio connection between the UE and the eNodeB is called Uu. Through S1, the eNodeB carries user-plane traffic to the Serving Gateway and Packet Data Network Gateway and control-plane signaling with the MME.

The eNodeB implements the RAN functions such as scheduling, radio resource management, HARQ, MIMO processing, and mobility management. It also performs security-related processing on the air interface and handles admission control and measurement collection for handover decisions.

In deployment, an eNodeB may be a single compact unit or part of a distributed RAN (D-RAN) or centralized RAN (C-RAN) where baseband processing is centralized in a BBU pool and remote radio heads provide RF transmission. The eNodeB participates in handovers with X2 interfaces to neighboring eNodes, facilitating seamless mobility.

Compared with 3G NodeB, the eNodeB has more integrated control and user plane functionality and tighter integration with the EPC. It is specified by 3GPP standards and forms the primary radio access node in LTE networks.